Activation of Ca(2+)-dependent K+ channels by cyanide in guinea pig adrenal chromaffin cells.
The effects of cyanide (CN) on whole cell current measured with the perforated-patch method were studied in adrenal medullary cells. Application of CN produced initially inward and then outward currents at -52 mV or more negative. As the membrane potential was hyperpolarized, amplitude and latency of the outward current (Io) by CN became small and long, respectively. A decrease in the external Na+ concentration did not affect the latency for CN-induced Io but enhanced the amplitude markedly. The CN Io reversed polarity at -85 mV, close to the Nernst potential for K+, and was suppressed by the K+ channel blockers curare and apamin but not by glibenclamide, suggesting that Io is due to the activation of Ca(2+)-dependent K+ channels. Consistent with this notion, the Ca(2+)-mobilizing agents, muscarine and caffeine, also produced Io. Exposure to CN in a Ca(2+)-deficient medium for 4 min abolished caffeine- or muscarine-induced Io without development of Io, and addition of Ca2+ to the CN-containing solution induced Io. We conclude that exposure to CN produces Ca(2+)-dependent K+ currents in an external Ca(2+)-dependent manner, probably via facilitation of Ca2+ influx.
Inoue
M
M
Department of Physiology, School of Medicine, Fukuoka University, Japan.
Imanaga
I
I
D000313:Adrenal Medulla / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001030:Apamin / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D003486:Cyanides / Q000494:pharmacology*; D005260:Female; D005905:Glyburide / Q000494:pharmacology; D006168:Guinea Pigs; D008564:Membrane Potentials / Q000187:drug effects; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D024683:Potassium Channels, Tandem Pore Domain; D013997:Time Factors
D003486:Cyanides; D015221:Potassium Channels; D024683:Potassium Channels, Tandem Pore Domain; D001030:Apamin; D002110:Caffeine; D005905:Glyburide; D002118:Calcium